There is a growing need for structures that provide personal protection against toxic chemical and biological agents. It is known to devise structures that are impermeable to toxic chemical vapors and liquids, but, when used as apparel, such structures are typically also hot, heavy and uncomfortable to wear.
The degree of comfort offered by apparel worn as a protective suit is significantly affected by the amount of water vapor that can permeate through the fabric from which the suit is made. The human body continuously perspires water as a method for controlling body temperature. When a protective fabric hinders the loss of water vapor from the body, the transpirational cooling process is hindered, which leads to personal discomfort. When a protective suit allows little or no loss of water vapor, extreme heat stress or heat stroke can result in a short period of time. Hence, it is desirable that, in addition to offering the highest levels of protection against toxic chemicals and liquids, a practical chemical and biological protective suit has relatively high water vapor transmission rates. It is also desirable that the appropriate protective structure be relatively light in weight and offer the same level of protection over a long period of time.
Co-pending U.S. patent application Ser. No. 10/883,105 discloses ballistic fabric articles and protective gear comprising aramid, polybenzazole or high performance polyethylene fibers treated with a solution containing a chitosan agent to render the articles antimicrobial, thereby preventing the development of odor, and fungal and bacterial growth. The chitosan agent can be applied to the article directly, to the fiber or as a fabric finish.
In co-pending U.S. patent application Ser. No. 11/593,958, selectively permeable laminates that contain a continuous chitosan film and that can be used in articles for personal protection, providing improved wearer comfort compared with impermeable articles are disclosed.
There remains a need for chitosan films with reduced shrinkage for use in structures including laminates.